Association between vitamin D receptor gene polymorphisms and fasting idiopathic hypercalciuria in recurrent stone-forming patients

A functional MMP-9-1562C>T polymorphism, MMP-9 serum levels and nephrolithiasis risk in a southern Chinese population

Background

The role of matrix metalloproteinase 9 (MMP-9) in the pathophysiology of chronic kidney disease (CKD), which is associated with a nearly two-fold greater risk for urinary calculi compared to people without CKD, has been demonstrated. The aim of the research is to evaluate the association between MMP-9-1562C>T polymorphism, MMP-9 serum levels and nephrolithiasis risk.

Methods

A hospital-based case-control study involving 302 kidney stone patients and 408 controls without kidney stone from southern China was conducted. Sanger sequencing was used to genotype the MMP-9-1562C>T polymorphism. The serum MMP-9 was measured in 105 kidney stone patients and 77 controls by enzyme-linked immunosorbent assay.

Results

Compared to the control group, the CT genotype was more frequent in nephrolithiasis patients (adjusted OR = 1.60, 95% CI = 1.09-2.37: the risk of developing nephrolithiasis in individuals with CT genotype compared to CC genotype). Moreover, there was also a higher frequency of CT/TT genotypes among patients with nephrolithiasis (adjusted OR = 1.49, 95% CI = 1.02-2.19: the risk of developing nephrolithiasis in individuals with CT/TT genotypes compared to CC genotype). The risk remained for the subgroups of patients aged >53, smokers with pack-years of smoking >20, non-drinkers, non-diabetic patients, patients with hypertension, recurrent episodes and calcium oxalate stones (OR = 2.26, 95% CI = 1.31-3.91; OR = 5.47, 95% CI = 1.10-27.30; OR = 1.76, 95% CI = 1.14-2.72; OR = 1.54, 95% CI = 1.03-2.30; OR = 1.97, 95% CI = 1.01-3.82; OR = 1.67, 95% CI = 1.06-2.62; OR = 1.54, 95% CI = 1.02-2.32, respectively). Biochemical parameters did not differ between genotypes. Compared to controls (18.57 ± 5.80 ng/mL), nephrolithiasis patients had significantly higher serum MMP-9 levels (30.17 ± 6.78 ng/mL, p < 0.001). The serum MMP-9 levels of patients with CT/TT genotypes of MMP-9-1562C>T were significantly higher than those with CC genotype (32.00 ± 6.33 vs. 29.13 ± 6.85 ng/mL, p = 0.037).

Conclusion

The MMP-9-1562C>T polymorphism in association with its soluble protein increased the risk of kidney stone, thus suggesting it could be used as a susceptibility biomarker for nephrolithiasis. Further functional studies and larger studies that include environmental exposure data are needed to confirm the findings.

Genetic Polymorphisms and Kidney Stones Around the Globe: A Systematic Review and Meta-Analysis

Objective: This study explores associations between recurrent kidney stones and genetic polymorphisms.

Methods: Meta-analysis of polymorphisms in renal stone cases versus control groups. Four electronic databases (PubMed, SCOPUS, EMBASE, and Web of Science) were searched up to 30 May 2021, using the keywords: “kidney stone” or “kidney calculi,” or “urolithiasis” or “nephrolithiasis” or “urinary calculi” and “genome” or “genetic” or “mutation” or “single nucleotide polymorphism.” Forrest plots, ORs, 95% CI, Chi-square (χ2)-test, and index of heterogeneity (I2) were calculated. Only studies with Newcastle–Ottawa scale (NOS) ≥ 6 were included for quality control, and Funnel, Begg’s, and Eager’s plots assessed publication bias. PROSPERO: CRD42022250427.

Results: Among 7,671 searched articles, 72 were included. Polymorphisms in VDR (OR: 1.20; 95% CI: 1.06–1.36), CASR (OR = 1.24; 95% CI: 1.01–1.52), Osteopontin (OR = 1.38; 95% CI: 1.09–1.74), and Urokinase genes (OR = 1.52; 95% CI: 1.02–2.28) showed a significant association with risk of urinary stone formation, while Klotho gene showed a protective effect (OR = 0.75; 95% CI: 0.57–0.99). The VDR gene polymorphism was frequent in Asians, whereas CASR polymorphism was frequent in European and North American populations.

Conclusion: Multifactorial nature of the stone formation, emphasizing the role of environmental factors, might explain contradictory results in the literature. While polymorphisms in VDR, CASR, Osteopontin, and Urokinase genes were associated with urinary stone formation, the Klotho gene showed a protective effect.

CAG repeats and one polymorphism in androgen receptor gene are associated with renal calcium stone disease

PURPOSE

Evidence suggests that androgens can be involved in the pathogenesis of renal stones. This study aimed at investigating coding region polymorphisms and CAG repeats in androgen receptor (AR) and their association with active renal calcium stone disease.

MATERIALS AND METHODS

Male patients with calcium kidney stones (N = 106) with at least two episodes of stone recurrence or size increase during the past 5 years (ASF) were enrolled from December 2008 to April 2009. Control individuals were recruited after matching for age and gender from healthy individuals without current stone or history of stone disease. Genetic sequencing and single strand conformational polymorphism (SSCP) were used to determine AR polymorphisms in the patients and controls.

RESULTS

Two polymorphisms were identified in the AR gene: Silent G to A polymorphism in the first exon of the AR gene and C to G polymorphism in intron 4. CAG repeats ranged from 12 to 37. The C/G polymorphism in intron 4 and CAG repeats were associated with the status of active renal calcium stone disease (all p < 0.05). The CC variant of C/G polymorphism was not observed in patients with stone disease. CAG repeats less than 20 and more than 28 were mostly observed in ASF patients (p < 0.05).

CONCLUSIONS

CAG repeats and intron 4 C/G polymorphism in the AR gene have an association with renal calcium stone disease.

Genetic polymorphisms as prognostic factors for recurrent kidney stones: A systematic review and meta-analysis

Genetic polymorphisms have been suggested as risk factors affecting the occurrence and recurrence of kidney stones, although findings regarding the latter remain inconclusive. We performed this systematic review and meta-analysis to clarify the associations between genetic polymorphisms and recurrent kidney stones. PubMed, SCOPUS, EMBASE, and Cochrane Library databases were searched through May 28^th, 2020 to identify eligible studies. The Quality in prognostic studies (QUIPS) tool was used to evaluate bias risk. Allelic frequencies and different inheritance models were assessed. All analyses were performed using Review manager 5.4. A total of 14 studies were included for meta-analysis, assessing urokinase (ApaL1) and vitamin D receptor (VDR) (ApaI, BsmI, FokI, and TaqI) gene polymorphisms. The ApaLI polymorphism demonstrated protective association in the recessive model [odds ratio (OR) 0.45, P < 0.01] albeit higher risk among Caucasians in the heterozygous model (OR 16.03, P < 0.01). The VDR-ApaI polymorphism showed protective association in the dominant model (OR 0.60, P < 0.01). Among Asians, the VDR-FokI polymorphism recessive model showed significant positive association (OR 1.70, P < 0.01) and the VDR-TaqI polymorphism heterozygous model exhibited protective association (OR 0.72, P < 0.01). The VDR-BsmI polymorphism was not significantly associated with recurrent kidney stones in any model. Urokinase-ApaLI (recessive model), VDR-ApaI (dominant model), and VDR-TaqI (heterozygous model) polymorphisms were associated with decreased recurrent kidney stone risk whereas urokinase-ApaLI (heterozygous model) and VDR-FokI polymorphisms were associated with increased risk among Caucasians and Asians, respectively. These findings will assist in identifying individuals at risk of kidney stone recurrence.

Idiopathic Osteoporosis and Nephrolithiasis: Two Sides of the Same Coin?

Idiopathic osteoporosis and nephrolithiasis are formidable health problems showing a progressive increase in their incidence and prevalence in the last decades. These temporal trends were observed in both pediatric and adult populations worldwide. Epidemiological and experimental studies indicate that both disorders show several common pathogenic environmental and genetic factors. In this review, we analyzed the clinical characteristics common to the two disorders and the state-of-the-art knowledge regarding the genetic predisposition and the environmental factors recognized as triggers in adult and pediatric ages. As a result of this work, we propose to consider idiopathic nephrolithiasis and osteoporosis as two possible expressions of a unique clinical syndrome. Accordingly, the clinical approach to both disorders should be modified in order to program an efficient primary and secondary prevention strategy.

Vitamin D receptor gene polymorphisms and susceptibility to urolithiasis: a meta-regression and meta-analysis

BACKGROUND

The currently available data with respect to the association between vitamin D receptor (VDR) gene polymorphism and risk to urolithiasis are inconclusive and inconsistent. Hence, an exhaustive meta-analysis can solve the discrepancies and provide a hint for upcoming investigations. Herein, a meta-analysis was carried out to attain a conclusive estimate of the association between VDR gene single nucleotide polymorphisms (SNPs) and urolithiasis risk.

METHODS

The major databases, including ISI Web of science, Scopus, and PubMed/MEDLINE were searched systematically from until June 2020 to retrieve all relevant studies. Association between VDR gene polymorphisms, including FokI (rs2228570), TaqI (rs731236), BsmI (rs1544410), and ApaI (rs7975232), and urolithiasis risk was evaluated using pooled odds ratio (OR) and their corresponding 95% confidence interval (CI). Additionally, to seek for the potential source of heterogeneity, meta-regression analyses were exerted.

RESULTS

Literature search led to finally finding of 33 studies evaluating the VDR gene SNPs and urolithiasis risk. It was observed that none of the four SNPs were significantly associated with urolithiasis predisposition. However, subgroup analysis confirmed higher risk of urolithiasis in East-Asian and Caucasian population with ApaI and TaqI gene polymorphism. The analyses of sensitivity acknowledged the results stability.

CONCLUSION

Although this meta-analysis did not support the association of FokI, TaqI, BsmI, and ApaI in the overall polled analysis, it suggests that ApaI and TaqI SNPs is associated with increased risk of urolithiasis in East-Asian and Caucasians populations.

Relationship Between the ApaI (rs7975232), BsmI (rs1544410), FokI (rs2228570), and TaqI (rs731236) Variants in the Vitamin D Receptor Gene and Urolithiasis Susceptibility: An Updated Meta-Analysis and Trial Sequential Analysis

The relationship between urolithiasis and vitamin D receptor (VDR) gene variants is still under debate according to the available published literature. To assess correlations between VDR gene variants ApaI (rs7975232), BsmI (rs1544410), FokI (rs2228570), and TaqI (rs731236) and urolithiasis susceptibility, we performed the present study through meta-analysis. The PubMed, Cochrane Library, China National Knowledge Infrastructure, EMBASE, Web of Science, and Wanfang databases were searched to retrieve qualified case-control studies. Finally, 31 reports were selected for the present meta-analysis. The results demonstrated that the VDR gene TaqI TT genotype was related to decreased risk of urolithiasis in the overall population (TT vs. Tt+tt: P = 0.011, OR = 0.824, 95% CI = 0.709–0.957). In ethnicity subgroup analysis, we found that the TaqI variant was obviously correlated to urolithiasis risk among Asians and Caucasians (P < 0.05). Additionally, significant urolithiasis risk was identified in adults. However, the FokI, BsmI, and ApaI variants did not have an increased risk of developing urolithiasis. Trial sequential analysis results were on a sufficiently large number of participants and did not require more research to confirm associations. Our research suggested that the VDR gene variant TaqI was correlated with urolithiasis susceptibility and that the t-allele might be the risk gene and T-allele the protective gene in VDR TaqI variant.

Vitamin D Status in Paget Disease of Bone and Efficacy-Safety Profile of Cholecalciferol Treatment in Pagetic Patients with Hypovitaminosis D

Adequate vitamin D status is essential for skeletal health. Paget's disease of bone (PDB) is a common metabolic skeletal disorder, but data regarding the vitamin D status in PDB patients are lacking. We performed a case-control study to estimate vitamin D status in 708 PDB patients and in 1803 healthy controls from Italy and an observational prospective study to evaluate the efficacy-safety profile of oral cholecalciferol treatment [400.000 International Units (UI) of cholecalciferol administered in cycles of 8 weeks until 25OHD levels reaches 70 nmol/L as primary therapy and 50.000 UI of cholecalciferol administered every 2 weeks for 52 weeks for the maintenance therapy] in 82 PDB patients with hypovitaminosis D, i.e., 25OHD < 50 nmol/L. The main outcome measures for the prospective study were 25OHD levels, metabolic risk factors (RF) for nephrolithiasis, bone pain score (BPS), and pain medication score (PMS). Over half of PDB patients had hypovitaminosis D. Among PDB patients treated with cholecalciferol, 76 patients reached 25OHD levels ≥ 70 nmol/L after the first cycle of primary therapy and the remaining six patients after a second cycle. The maintenance therapy guaranteed 25OHD levels ≥ 70 nmol/L during the entire follow-up. The increase in 25OHD levels reduced PTH, BPS, and PMS levels, without changes in RF for nephrolithiasis. We can conclude that (i) hypovitaminosis D is frequent in PDB patients, (ii) cholecalciferol significantly increased 25OHD levels in PDB patients, and (iii) the correction of hypovitaminosis D improves the quality of life of PDB patients without inducing significant changes in RF for nephrolithiasis.

Association of vitamin D receptor gene polymorphisms and risk of urolithiasis: results of a genetic epidemiology study and comprehensive meta-analysis

Polymorphisms of vitamin D receptor (VDR) gene have been associated with risk of urolithiasis, but, with inconsistent results and lack data from Pakistani population. Therefore, after including our indigenous study data, a comprehensive meta-analysis was performed to provide an evidence-based estimate of any association between VDR polymorphisms and urolithiasis risk. A total of 483 Pakistani subjects, comprising 235 urolithiasis patients and 248 healthy controls, were genotyped for 6 VDR polymorphisms. Additionally, a systematic literature search with subsequent meta-analysis was conducted and pooled odds ratios (ORs) were used to determine the strength of any existent associations. Trial sequential analysis (TSA) was also performed. Results revealed no significant association of any VDR polymorphism and urolithiasis risk in indigenous Pakistani patients. However, meta-analysis of 29 relevant studies indicated that VDR FokI polymorphism significantly increased the risk of urolithiasis in allelic (f vs. F: OR = 1.13; 95% CI = 1.05-1.22; p ≤ 0.01) and recessive (ff vs. FF + Ff: OR = 1.20; 95% CI = 1.05-1.38; p = 0.01) models with no significant heterogeneity. No associations were evident for VDR ApaI, BsmI and TaqI polymorphic variants and urolithiasis risk after correction for multiple testing. Subgroup analysis by ethnicity suggested significant association for FokI variant among Asians. The TSA results demonstrated that the evidence reflecting association of FokI polymorphism and urolithiasis risk was sufficient and conclusive. In conclusion, this meta-analysis suggests that VDR FokI polymorphism is significantly associated with urolithiasis risk, especially in Asians, whereas ApaI, BsmI and TaqI polymorphisms are not associated.

Polymorphisms of the VDR gene in patients with nephrolithiasis in a Han Chinese population

An association study between VDR gene polymorphisms and nephrolithiasis was conducted in different populations, but it is not yet known whether the association exists in the Han Chinese population. Here, we genotyped three SNPs (rs731236, rs7975232 and rs10735810) in the promoter region of the VDR gene by iMLDR genotyping assays in a large case-control cohort. The results demonstrated that there was no association found between the three SNPs (rs731236, rs7975232 and rs10735810) in the VDR gene and nephrolithiasis, whether in allele or genotype distribution. However, SNP rs10735810 was correlated with the level of serum calcium in control groups, but not in patient groups. In conclusion, considering the large sample size, we believe that the SNP rs10735810 allele A in the VDR gene promoter region may influence the level of serum calcium, but not influence the formation of nephrolithiasis in a Han Chinese population.

ApaL1 urokinase and Taq1 vitamin D receptor gene polymorphisms in first-stone formers, recurrent stone formers, and controls in a Caucasian population

The purpose of this study was to determine differences in genotype distribution and allele frequency of urokinase and vitamin D receptor (VDR) single nucleotide polymorphisms (SNPs) between first-stone formers, recurrent stone formers, and controls in a Caucasian population. A total of 86 first-stone formers, 78 recurrent stone formers, and 167 controls were included. Urokinase and VDR SNPs were tested by gene amplification followed by ApaL1 and Taq1 endonuclease digestion, respectively. Baseline variables, genotype, and allele frequencies were compared between the three groups, using descriptive statistics. Adjusted odds ratios were calculated to estimate the risk for recurrent urolithiasis associated with genotypes. We found that differences in the distribution of ApaL1 SNP and Taq1 SNP genotypes were statistically different between recurrent stone formers and first-stone formers, and between recurrent stone formers and controls. Allele frequency analysis showed that the T allele for ApaL1 SNP and the C allele for Taq1 SNP were significantly associated with recurrent urolithiasis. For Taq1 SNP, logistic regression analysis showed that the C/C genotype was associated with a more than threefold higher risk for recurrent urolithiasis. We conclude that ApaL1 and Taq1 SNPs of the urokinase and VDR genes are associated with recurrent urolithiasis in a Caucasian population.

Demographics and characterization of 10,282 Randall plaque-related kidney stones: a new epidemic?

Renal stone incidence has progressively increased in industrialized countries, but the implication of Randall plaque in this epidemic remains unknown. Our objectives were to determine whether the prevalence of Randall plaque-related stones increased during the past decades after having analyzed 30,149 intact stones containing mainly calcium oxalate since 1989 (cross-sectional study), and to identify determinants associated with Randall plaque-related stones in patients (case-control study). The proportion of Randall plaque-related stones was assessed over 3 time periods: 1989-1991, 1999-2001, and 2009-2011. Moreover, we analyzed clinical and biochemical parameters of 105 patients affected by calcium oxalate stones, with or without plaque. Of 30,149 calcium oxalate stones, 10,282 harbored Randall plaque residues (34.1%). The prevalence of Randall plaque-related stones increased dramatically during the past years. In young women, 17% of calcium oxalate stones were associated with Randall plaque during the 1989-1991 period, but the proportion rose to 59% 20 years later (P < 0.001). Patients with plaques experienced their first stone-related event earlier in life as compared with those without plaque (median age 26 vs 34 years, P = 0.02), had increased ionized serum calcium levels (P = 0.04), and increased serum osteocalcin (P = 0.001) but similar 25-hydroxyvitamin D levels. The logistic regression analysis showed that age (odds ratio [OR] 0.96, confidence interval [CI] 0.926-0.994, P = 0.02), weight (OR 0.97, CI 0.934-0.997, P = 0.03), and osteocalcin serum levels (OR 1.12, CI 1.020-1.234, P = 0.02) were independently associated with Randall plaque. The prevalence of the FokI f vitamin D receptor polymorphism was higher in patients with plaque (P = 0.047). In conclusion, these findings point to an epidemic of Randall plaque-associated renal stones in young patients, and suggest a possible implication of altered vitamin D response.

Association of vitamin D receptor BsmI (rs1544410), Fok1 (rs2228570), TaqI (rs731236) and ApaI (rs7975232) gene polymorphism with the nephrolithiasis susceptibility

Association of vitamin D receptor (VDR) gene polymorphism with the risk of nephrolithiasis from the published reports is still conflicting. This study was conducted to evaluate the relationship between VDR BsmI (rs1544410), Fok1 (rs2228570), TaqI (rs731236) and ApaI (rs7975232) gene polymorphism and the risk of nephrolithiasis using meta-analysis method. The association studies were identified from PubMed, and Cochrane Library on 1 April 2014, and eligible investigations were included and synthesized using meta-analysis method. Six reports were recruited into this meta-analysis for the association of VDR BsmI, Fok1, TaqI and ApaI gene polymorphism with nephrolithiasis susceptibility. In this meta-analysis, VDR BsmI, Fok1, TaqI and ApaI gene polymorphism were not associated with nephrolithiasis susceptibility for overall populations and in Caucasians. However, the Fok1 f allele and ff genotype were associated with the risk of nephrolithiasis in Asians, but the FF genotype not. Furthermore, TaqI TT genotype was associated with the risk of nephrolithiasis in Asians, but the t allele and tt genotype not. However, ApaI gene polymorphism was not associated with nephrolithiasis susceptibility in Asians. In conclusion, VDR BsmI, Fok1, TaqI and ApaI gene polymorphism were not associated with nephrolithiasis risk in overall populations and in Caucasians. But, the Fok1 f allele and ff genotype, TaqI TT genotype, ApaI gene polymorphism were associated with the risk of nephrolithiasis in Asians. However, more studies should be conducted to confirm it.

Effects of vitamin D receptor polymorphisms on urolithiasis risk: a meta-analysis

Background

Several studies analyzed the associations of Vitamin D receptor (VDR) polymorphisms with urolithiasis risk in different ethnic groups. However, the results were inconclusive. To evaluate a more precise estimation of the relationship, a meta-analysis was performed.

Methods

Pubmed, EMBASE, Wanfang Database, China National Knowledge Infrastructure (CNKI) and Weipu Database were searched. Data were extracted independently by two investigators. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations.

Results

Twenty-three case–control studies were included in this meta-analysis. Significant associations between ApaI, BsmI, FokI, and TaqI polymorphisms and urolithiasis risk were observed. However, sensitivity analyses for BsmI and FokI polymorphisms indicated that the results were not reliable and credible. In addition, there was a significant association of the ApaI-TaqI haplotype with urolithiasis risk.

Conclusions

This meta-analysis suggested that ApaI and TaqI polymorphisms in VDR gene were associated with urolithiasis risk.

The relation between bone and stone formation

Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.

The -160C>a polymorphism in E-cadherin is associated with the risk of nephrolithiasis

Nephrolithiasis is a common disorder worldwide. E-cadherin (CDH1) is involved in epithelial cell-cell interactions and plays important roles in the etiology of nephrolithiasis. We hypothesized that variants in the CDH1 gene are associated with risk of nephrolithiasis. In a hospital-based case-control study of 127 nephrolithiasis patients and 152 controls frequency matched by age and sex, we genotyped the functional -160C>A (rs16260) polymorphism and assessed its associations with risk of nephrolithiasis in a Chinese population. We found that the CA/AA genotypes were associated with a significantly decreased risk of nephrolithiasis (OR = 0.53, 95%CI = 0.32-0.87), compared with the CC genotype, particularly among subgroups of BMI > 24 kg/m² (OR = 0.38, 95%CI = 0.17-0.85), age ≤ 57 years (OR = 0.47, 95%CI = 0.24-0.93), and men (OR = 0.56, 95%CI = 0.29-0.99). Our results suggest that the CDH1 polymorphism is involved in the etiology of nephrolithiasis and thus may be a marker for genetic susceptibility to nephrolithiasis.

Characteristic clinical and biochemical profile of recurrent calcium-oxalate nephrolithiasis in patients with metabolic syndrome

BACKGROUND

Metabolic syndrome is a risk factor for nephrolithiasis. This study was performed to evaluate the clinical and biochemical profile of calcium-oxalate nephrolithiasis in stone formers with metabolic syndrome.

METHODS

A total of 526 recurrent stone formers, 184 of them with metabolic syndrome, and 214 controls were examined on a free diet and after a sodium-restricted diet (sodium intake < 100 mmol/24 h).

RESULTS

On free diet, stone formers with metabolic syndrome showed higher sodium excretion [mean (95% confidence interval), 196 (176-218) vs 160 (150-168) mmol/24 h; P < 0.01] and lower citrate excretion [2.23 (1.99-2.58) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls, whereas stone formers without metabolic syndrome showed higher calcium and oxalate excretion [5.43 (5.01-5.82) vs 3.58 (2.84-4.19) and 0.34 (0.32-0.36) vs 0.26 (0.20-0.31)m mmol/24 h for calcium and oxalate, respectively; P < 0.01] and lower citrate excretion [2.18 (1.98-2.38) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls. The ion activity product of urinary calcium-oxalate salts was similar between stone formers with and without metabolic syndrome [1.41 (1.31-1.59) vs 1.40 (1.35-1.45); P > 0.05]. After the test diet, this index was lower in diet-compliant stone formers with metabolic syndrome compared to diet-compliant stone formers without metabolic syndrome [1.15 (1.10-1.21) vs 1.39 (1.31-1.45); P < 0.01].

CONCLUSIONS

The biochemical profiles and responses to the sodium-restricted diet were significantly different between stone formers with metabolic syndrome and those without. Dietary habits play a central role in the pathogenesis of nephrolithiasis in stone formers with metabolic syndrome.

Polymorphisms in the vitamin D receptor and the androgen receptor gene associated with the risk of urolithiasis

Transcriptional activity of the vitamin D receptor (VDR) gene is regulated by androgen receptor (AR) gene and both are associated with renal stone formation. We examined gene polymorphisms of VDR (PCR-RFLP) and AR (GeneScan analysis) in 125 stone formers and 150 controls from north India. Genotype Ff of Fok-I and Tt of Taq-I demonstrated significantly higher risk (P<0.001, OR=3.559 and P=0.019, 1.830 respectively). Variant f allele exhibited 1.7-folds higher risk. Ff of Fok-I and Aa of Apa-I gene polymorphism showed higher risk in males only. Mean CAG repeat was significantly higher in hypercalciuric patients as compared to normocalciuric (mean=21.62 ± 3.384 vs. 20.11 ± 3.182; P=0.034). Combined effects 1.8-folds higher risk in patients with Tt genotype of Taq-I and short CAG repeat. Thus, association of FokI and TaqI VDR gene polymorphisms suggest VDR as an important genetic marker for urolithiasis. Further, patients with combination of Tt of Taq-I and short CAG repeat were at higher risk for stone formation.

Genetic basis of renal cellular dysfunction and the formation of kidney stones

Nephrolithiasis is a result of formation and retention of crystals within the kidneys. The driving force behind crystal formation is urinary supersaturation with respect to the stone-forming salts, which means that crystals form when the concentrations of participating ions are higher than the thermodynamic solubility for that salt. Levels of supersaturation are kept low and under control by proper functioning of a variety of cells including those that line the renal tubules. It is our hypothesis that crystal deposition, i.e., formation and retention in the kidneys, is a result of impaired cellular function, which may be intrinsic and inherent or triggered by external stimuli and challenges. Cellular impairment or dysfunction affects the supersaturation, by influencing the excretion of participating ions such as calcium, oxalate and citrate and causing hypercalciuria, hyperoxaluria or hypocitraturia. The production and excretion of macromolecular promoters and inhibitors of crystallization is also dependent upon proper functioning of the renal epithelial cells. Insufficient or ineffective crystallization modulators such as osteopontin, Tamm-Horsfall protein, bikunin, etc. are most likely produced by the impaired cells.

Vitamin D receptor polymorphisms are associated with increased susceptibility to primary biliary cirrhosis in Japanese and Italian populations

BACKGROUND/AIMS

Vitamin D receptor (VDR) agonists have recently been identified as potent immunomodulators capable of inhibiting Th1-mediated immune response, leading us to consider the hypothesis that functional VDR polymorphisms might contribute to enhanced risk for developing primary biliary cirrhosis (PBC), a Th1-mediated autoimmune disease. In the current study, we aimed at elucidating the genetic association of VDR polymorphisms with susceptibility to PBC in Japanese and Italian populations.

METHODS

We enrolled 334 PBC patients (195 Japanese and 139 Italians), as well as 334 age- and sex-matched controls (179 Japanese and 156 Italians). VDR genotyping was performed by PCR-RFLP, using BsmI, ApaI and TaqI endonucleases.

RESULTS

The genotype BB of BsmI polymorphism was significantly associated with PBC (OR = 1.80 [95% CI; 1.19-2.73], p = 0.005). The association of the genotype BB was observed in Japanese (OR = 13.77, p = 0.001), and Italians (OR = 1.83, p = 0.019), respectively, although not significant in Italians after Bonferroni correction. The frequency of the B allele at the BsmI polymorphism was significantly higher in PBC patients (OR = 1.27 [95% CI; 1.02-1.59], p = 0.040).

CONCLUSIONS

The genotype 'BB' as well as 'B' allele at BsmI polymorphism of the VDR gene contribute to the risk of PBC development.

Association between metabolic syndrome and nephrolithiasis in an inpatient population in southern Italy: role of gender, hypertension and abdominal obesity

BACKGROUND

Metabolic syndrome (MetS) and nephrolithiasis (NL) are quite common disorders. While some of the components of MetS have been proposed as precursors of NL in population studies, no data are available about the possible association between NL and MetS as such. The primary objective of the study was to evaluate the relationship between MetS and NL. The secondary outcome was to examine the relationship between MetS single constitutive elements and NL considering the strict correlation occurring among these factors.

METHODS

We studied 2132 Caucasian inpatients of the 'Spinelli' Hospital in southern Italy (males/females = 0.95; mean age 63.8 +/- 15.8 years; body mass index 26.1 +/- 3.9 kg/m(2)). The MetS diagnosis was performed according to the Heart Association/National Heart, Lung, and Blood Institute criteria. The presence of NL was assessed by ultrasound examination of the kidneys and upper urinary tract.

RESULTS

Seven hundred twenty-five subjects (34.0%) had a positive diagnosis of MetS. Two hundred twenty subjects (10.3%) had echographic evidence of NL, while 199 subjects reported a past history of NL (9.3%). The presence of MetS, as well as the male sex, and the occurrence of a previous episode of NL (in male subjects only) were each independently related to echographic evidence of NL. Among the individual components of MetS, high blood pressure and abdominal obesity (in female individuals only) were also independently related to echographic evidence of NL.

CONCLUSIONS

MetS is significantly associated with echographic evidence of NL. A gender-related difference in the clinical expression of NL was also observed.

New insights into the pathogenesis of idiopathic hypercalciuria

Idiopathic hypercalciuria (IH) is the most common metabolic abnormality in patients with calcium kidney stones. It is characterized by normocalcemia, absence of diseases that cause increased urine calcium, and calcium excretion that is greater than 250 mg/d in women and 300 mg/d in men. Subjects with IH have a generalized increase in calcium turnover, which includes increased gut calcium absorption, decreased renal calcium reabsorption, and a tendency to lose calcium from bone. Despite the increase in intestinal calcium absorption, a negative calcium balance is seen commonly in balance studies, especially on a low-calcium diet. The mediator of decreased renal calcium reabsorption is not clear; it is not associated with either an increase in filtered load of calcium or altered parathyroid hormone levels. There is an increased incidence of hypercalciuria in first-degree relatives of those with IH, but IH appears to be a complex polygenic trait with a large contribution from diet to expression of increased calcium excretion. Increased tissue vitamin D response may be responsible for the manifestations of IH in at least some patients.

Predisposition of genetic polymorphism with the risk of urolithiasis

Urolithiasis is a relevant clinical problem with a subsequent burden for health system. The aim of this review is to provide recent progress made using genetic polymorphisms to define pathophysiology, to identify persons at risk for kidney stone disease and to predict treatment response. Population case-control studies are useful both as an alternative and an adjunct as compared to family studies. These involve either whole genome scanning or candidate gene approaches. While whole genome scanning is likely to be widely used in future, at present, candidate gene studies are more feasible. When performing candidate gene case-control studies factors such as study design, methods for recruitment of case and controls, selection of candidate genes, functional significance of polymorphisms chosen for study and statistical analysis require close attention to ensure that only genuine associations are detected. Some of the significant genes that play role in stone formation include calcitonin receptor gene (CTR), vitamin D receptor (VDR), Urokinase, Interleukin, (IL-1β, IL-Ra), E-Cadherin, Androgen & oestrogen receptor gene, vascular endothelial growth factor (VEGF) and Arginine p21. In our case-control study we studied CTR, VDR, Urokinase, IL-1β(-511 and +3954), IL-Ra from north India and predict that VDR, IL-β (-511) and IL-1Ra gene may be used as a possible genetic marker for earlier detection in patients who are at risk for calcium oxalate stone disease. Further, linkage disequilibrium and haplotype structure of a certain candidate gene is important for association analysis. When a certain polymorphic allele has been found to be associated with disease, it is further explained on basis of LD and haplotype structure by one or more other alleles. Once it is determined which haplotype carries the risk allele, by means of molecular biological functional analyses, the variants on that haplotype allele truly causing the effect can be determined.

Mechanisms and regulation of epithelial Ca2+ absorption in health and disease

Ca2+ is essential for numerous physiological functions in our bodies. Therefore, its homeostasis is finely maintained through the coordination of intestinal absorption, renal reabsorption, and bone resorption. The Ca2+-selective epithelial channels TRPV5 and TRPV6 have been identified, and their physiological roles have been revealed: TRPV5 is important in final renal Ca2+ reabsorption, and TRPV6 has a key role in intestinal Ca2+ absorption. The TRPV5 knockout mice exhibit renal leak hypercalciuria and accordingly upregulate their intestinal TRPV6 expression to compensate for their negative Ca2+ balance. In contrast, despite their severe negative Ca2+ balance, TRPV6-null mice do not display any compensatory mechanism, thus resulting in secondary hyperparathyroidism. These results indicate that the genes for TRPV5 and TRPV6 are differentially regulated in human diseases associated with disturbed Ca2+ balance such as hypercalciuria, osteoporosis, and vitamin D-resistant rickets.

Update on primary hypercalciuria from a genetic perspective

PURPOSE

This review provides a brief update on genetic studies of primary hypercalciuria. We consider their possible implications for the pathogenesis and complications of primary hypercalciuria.

MATERIALS AND METHODS

Using the PubMed, MEDLINE and Scopus databases we reviewed the literature on pathogenesis and the complications of hypercalciuria, giving particular attention to genetic studies in humans.

RESULTS

Primary hypercalciuria is a defect occurring in 5% to 10% of the general population and it is most commonly detected in patients with calcium kidney stones or osteoporosis. In children it is associated with hematuria, renal stones or nocturnal enuresis. Although high penetrance, autosomal dominant inheritance cannot be ruled out, hypercalciuria is probably a polygenic disorder. A number of genes have been suggested as candidates in the pathogenesis of common idiopathic calcium nephrolithiasis and hypercalciuria, ie soluble adenylate cyclase, calcium sensing receptor, vitamin D receptor, chloride channel-5, sodium-phosphate cotransporter-2 and claudin-16. These genes may also have a role in complications of hypercalciuria.

CONCLUSIONS

The classic distinction among absorptive, renal and resorptive hypercalciuria seems insufficient to explain the many cellular and tissue modifications observed in patients with primary hypercalciuria. The condition seems to be a separate disorder, characterized by altered calcium transport in the intestine, kidney and bone, and caused by various combinations of multiple genetic and dietary changes.

Association of vitamin D receptor (Fok-I) polymorphism with the clinical presentation of calcium urolithiasis

OBJECTIVE

To investigate the effect of the vitamin D receptor (VDR) FokI polymorphism on the clinical presentation of calcium urolithiasis, as a FokI polymorphism in the VDR gene was recently reported to be associated with calcium metabolism disorders.

PATIENTS, SUBJECTS AND METHODS

In all, 235 patients with calcium urolithiasis and 231 age- and sex-matched healthy controls were recruited from Kaohsiung Medical University Hospital between June 2003 and February 2005. Clinical information on the age at first onset, stone episodes, stone severity and presence of family history were collected from patients with stones. Any VDR FokI polymorphism was detected using polymerase chain reaction-based restriction analysis.

RESULTS

The frequency of VDR FokI genotypes between the patients and the healthy controls was not significantly different. However, among patients, those with the FF genotype had a significantly higher risk of having more stone episodes (adjusted odds ratio 2.15, 95% confidence interval 1.02-4.54, P = 0.044) and were younger at the first onset (3.23, 1.08-9.63, P = 0.036) than those with the ff genotype.

CONCLUSION

The VDR FokI polymorphism might be important in the clinical presentation of patients with calcium urolithiasis, especially for the frequency of stone episodes and age at first onset, although it is not associated with the formation of stones.

The positive effect of dietary vitamin D intake on bone mineral density in men is modulated by the polyadenosine repeat polymorphism of the vitamin D receptor

INTRODUCTION

Few studies have considered the dietary influence of vitamin D intake on bone mineral density (BMD). Numerous studies have examined the association between VDR polymorphism and BMD, but no previous study has examined the joint influence of dietary vitamin D intake and VDR polymorphism on BMD.

METHODS

We therefore conducted a study in 230 men aged 41-76 years of age. BMD was measured with DXA. A second bone scan was performed on average 2.7 years after the first investigation. Dietary habits were assessed by 14 dietary 24-h recall interviews. The polyadenosine (A) VDR genotypes were determined.

RESULTS

Dietary vitamin D intake was associated with BMD at all sites, also after multivariate adjustment. Those in the highest quintile of intake had 9% higher femoral neck BMD (p = 0.004), 6% higher BMD at the lumbar spine (p = 0.06) and 5% higher total body BMD (p = 0.003) compared to men in the lowest quintile of dietary vitamin D intake. However, the positive association between vitamin D intake and BMD was especially apparent among those with the L/L polyadenosine (A) VDR genotype explaining between 10 and 15% of the variability in BMD depending on site (p < 0.004). There was furthermore a trend, in the lumbar spine, of less reduction in BMD with increasing vitamin D intake (p = 0.07) but not at the other sites. Calcium intake conferred no association with BMD.

CONCLUSIONS

Our results indicate that the extent of positive association between dietary vitamin D intake and BMD in men is dependent on VDR polymorphism, a novel conceivable important gene-environmental interaction.

Bone disease in idiopathic hypercalciuria

PURPOSE OF REVIEW

Decreased bone mineral density and increased prevalence of bone fractures have been found in patients with idiopathic hypercalciuria. The purpose of this review is to summarize the recent published evidence that supports a potential role of the bone, and its link to the kidney and intestine, in the pathogenesis of idiopathic hypercalciuria. The effects of hypercalciuria on bone and the implications for treatment are also reviewed.

RECENT FINDINGS

Evidence suggests that the incidence of a first fracture in kidney stone patients is fourfold higher than the control population. Support for the role of bone in the pathophysiology of hypercalciuria has been corroborated. New studies have detailed the effects of several cytokines - increased number and sensitivity of vitamin D receptors, and increased acid production - upon the bone acting cells. Similarly, recent clinical and experimental studies have suggested that genetic factors confer a predisposition to the formation of renal calcium stones and bone demineralization.

SUMMARY

Whether hypercalciuria is the result of a primary bone disorder, a consequence of a persisting negative calcium balance or a combination of both still remains to be determined. Nevertheless, bone status must be evaluated and followed up in patients with idiopathic hypercalciuria.

The long-term outcomes of idiopathic hypercalciuria in children

OBJECTIVE

Idiopathic hypercalciuria (IH) is a metabolic risk factor in patients with urinary calcium stones and implicated in 30%-50% of all urinary stone diseases. Clinical manifestations and distribution of types of IH are reviewed, as well as current treatment methods and long-term outcomes.

PATIENTS

A total of 131 patients (70 boys and 61 girls), aged 1-15 years (mean 7.9+/-3.19 years), were studied. Follow up was between 6 months and 16 years (mean 4.1+/-6.8 years).

RESULTS

Fifty-three patients (40%) were diagnosed following calcium challenge as renal type, and 51 (39%) as absorptive type of hypercalciuria. Whereas 72 patients (54.9%) had a family history of nephrolithiasis, 59 patients did not. Nephrolithiasis was found in 27 patients (20%) on admission (absorptive=9.9%, renal=4.5%, undetermined=6.1%), but developed in eight other patients (6.1%) (absorptive=2.2%, renal=0.7%, undetermined=3.8%). Urinary calcium excretion reversed in 65 patients with the suggested diet therapy; it recurred in 30 patients (22.9%) (absorptive=9.1%, renal=11.4%, undetermined=2.2%) but 35 returned to normal definitively (26.7%) (absorptive=11.4%, renal=12.9%, undetermined=2.2%). No change was seen in the status of 50 patients (38.1%) (absorptive=18.3%, renal=16%, undetermined=3.8%).

CONCLUSION

IH may be accompanied by nephrolithiasis; type must be determined and those patients with absorptive type should be followed for nephrolithiasis. Our results suggest that formation of new stones could be prevented with diet and thiazide therapies in IH.

Fibroblast growth factor 23 is increased in calcium nephrolithiasis with hypophosphatemia and renal phosphate leak

CONTEXT

Nephrolithiasis affects about 10% of the population in industrialized countries, with calcium salts composing more than 80% of renal stones. A significant percentage of patients with calcium nephrolithiasis and normal parathyroid function show hypophosphatemia and reduced renal phosphate reabsorption (i.e. a renal phosphate leak).

OBJECTIVES

The objective of the study was to compare serum levels of fibroblast growth factor 23 (FGF23), a regulator of phosphate homeostasis, in 110 recurrent stone formers with or without renal phosphate leak, six patients affected by X-linked hypophosphatemic rickets, five patients affected by oncogenic osteomalacia, and 60 unrelated healthy controls.

DESIGN

This was a prospective interventional study.

METHODS

Renal phosphate leak was identified based on the occurrence of idiopathic hypophosphatemia [serum phosphate concentration < 2.50 mg/dl (<0.80 mmol/liter)] and reduced renal threshold phosphate concentration [<2.2 mg/liter (<0.70 mmol/liter)].

RESULTS

In 22 stone formers with renal phosphate leak, serum FGF23 concentration was significantly higher as compared with 88 stone formers without renal phosphate leak and with controls [83.3 (65.6-101.1) vs. 32.1 (26.8-37.4) and 24.5 (19.8-29.1) reference units (RU)/ml, respectively]. Stone formers with renal phosphate leak showed lower FGF23, compared with patients with oncogenic osteomalacia and X-linked hypophosphatemic rickets [572.3 (235.9-908.7) RU/ml]. Among stone formers and controls, serum FGF23 concentration displayed a strong inverse association with serum phosphate (r = -0.784, P = 0.009) and the rate of tubular phosphate reabsorption (r = -0.791, P = 0.008).

CONCLUSIONS

In our study population, renal phosphate leak affected 20% of stone formers and was strongly associated with increased serum FGF23 concentration.

Épidémiologie actuelle de la lithiase rénale en France

Nephrolithiasis is a frequent disease that affects about 10% of people in western countries. The prevalence of calcium oxalate stones has been constantly increasing during the past fifty years in France as well as in other industrialized countries. Stone composition varies depending to gender and age of patients and also underlines the role of other risk factors and associated pathologies such as body mass index and diabetes mellitus. The decrease in struvite frequency in female patients is the result of a significantly improved diagnostic and treatment of urinary tract infections by urea-splitting bacteria. In contrast, the increasing occurrence of weddellite calculi in stone forming women aged more than 50 years could be the consequence of post-menopausal therapy. A high prevalence of uric acid was found in overweight and obese stone formers and in diabetic ones as well. Another important finding was the increased occurrence with time of calcium oxalate stones formed from papillary Randall's plaques, especially in young patients. Nutritional risk factors for stone disease are well known: they include excessive consumption of animal proteins, sodium chloride and rapidly absorbed glucides, and insufficient dietary intake of fruits and potassium-rich vegetables, which provide an alkaline load. As a consequence, an excessive production of hydrogen ions may induce several urinary disorders including low urine pH, high urine calcium and uric acid excretion and low urine citrate excretion. Excess in calorie intake, high chocolate consumption inducing hyperoxaluria and low water intake are other factors, which favour excessive urine concentration of solutes. Restoring the dietary balance is the first advice to prevent stone recurrence. However, the striking increase of some types of calculi, such as calcium oxalate stones developed from Randall's plaque, should alert to peculiar lithogenetic risk factors and suggests that specific advices should be given to prevent stone formation.